MPs from all parties protested at Westminster this afternoon at attempts by lawyers acting for the oil trader Trafigura to stop reports of parliamentary proceedings.

The Labour MP Paul Farrelly told the speaker, John Bercow, attempts by lawyers Carter-Ruck to gag the media could be a "potential contempt of parliament".

The Liberal Democrat MP Evan Harris said there was a need to "control the habit of law firms" of obtaining secrecy injunctions, and his colleague David Heath told the Commons a "fundamental principle" was being threatened: that MPs should be able to speak freely and have their words reported freely.

On the Conservative side, David Davies criticised the rising use of "super-injunctions", in which the fact of the injunction is itself kept secret. He said courts should not be allowed to grant injunctions forbidding the reporting of parliament.

Bercow said the issue could be raised formally as a matter of privilege, but he understood the injunction had now been lifted.

Farrelly, who tabled a parliamentary question yesterday that the Guardian had been forbidden from reporting, told the Commons: "I want to raise a point of order regarding a chain of events which may be of concern to the House.

"Today, the Guardian reported that it had been prevented from reporting a written question tabled by a member of parliament. This morning, I telephoned the Guardian to ask whether the MP was myself.

"The question was printed on the order paper yesterday and relates to the activities of Trafigura, an international oil trader at the centre of a controversy regarding toxic waste-dumping in the Ivory Coast, and to the role of its solicitors, Carter-Ruck.

"Yesterday, I understand, Carter-Ruck, quite astonishingly, warned of legal action if the Guardian reported my question. In view of the seriousness of this, will you accept representations from me over this matter and consider whether Carter-Ruck's behaviour constitutes a potential contempt of parliament?"

Earlier, Trafigura's law firm had refused to alter an existing blanket court order banning the Guardian from mentioning Trafigura's recourse to the courts. This refusal was despite the publication on parliament's official website of Farrelly's questions revealing the facts,.

The result of Carter-Ruck's intransigence was an avalanche of online publication, as well as the reproduction of Farrelly's parliamentary questions in the magazine Private Eye, which hit the London streets at lunchtime today. Bloggers who posted Farrelly's questions in full included the political website Guido Fawkes and the Spectator magazine website.

Large numbers of messages were posted on Twitter, to the extent that "Trafigura" and "Carter-Ruck" became the most viewed keywords in London throughout the morning.

Shortly before the case was due to come to court, Carter-Ruck announced that its clients would no longer oppose reporting of what was said in parliament about them.

Farrelly told the Guardian afterwards: "The issuing by the courts of so-called super-injunctions is rightly controversial and a matter of growing concern. That is why, using parliamentary privilege, I tabled these questions to Jack Straw at the Ministry of Justice as a matter of urgency.

"The practice offends the time-honoured 'rule against prior restraint', which safeguards freedom of expression in this country. It also fails to protect whistleblowers acting in the public interest. The huge legal bills involved in fighting cases, too, have a chilling effect on legitimate investigative journalism.

"So often, the beneficiaries are big corporations. The fact that the press is also barred from reporting the existence of these gagging orders is doubly pernicious. It is a subject the select committee will be addressing in our current inquiry into the press and the way the law works in Britain today.

"Absolute privilege in reporting parliament has been established since the Bill of Rights in 1688. It is a fundamental freedom for the press, and it is vital that neither lawyers nor the courts seek to attack this time-honoured right."